Prevalence and genomic characterization of Salmonella Weltevreden in commercial pig feed.

Viet Nam is the world's fifth largest producer of pork meat. Salmonella is frequently found at farm level; however, risk factors for Salmonella infection in pigs have not been thoroughly investigated in the production system. In the current study, 123 commercial feed samples were obtained from 103 small, medium and large-scale pig farms in Viet Nam and investigated for the presence of Salmonella in 25 g of feed using the ISO 6579:2002/Cor 1:2004 method. Salmonella was detected in five samples (4.1%; 95% CI 1.75-9.16%). All five samples were found to contain S. Weltevreden as the only serovar. The isolates were subjected to phenotypic and whole genome sequencing analysis for further characterization. They all belonged to ST365 and were sensitive to the 14 antimicrobials tested. Four strains were found to belong to the continental lineage of S. Weltevreden, while one isolate was of the island type. This isolate, contrary to the remaining four isolates contained a prophage homolog to the Vibrio prophage X-29. The findings of only S. Weltevreden, which is often isolated from fish and aquatic samples, suggests that fishmeal used in the feed preparation was a likely source of contamination.

Occurrence, seasonality and genetic diversity of Vibrio vulnificus in coastal seaweeds and water along the Kii Channel, Japan.

Vibrio vulnificus is a ubiquitous toxigenic bacterium found in a coastal environment but little is known about its occurrence and seasonality among seaweeds, which are widely consumed as seafood in Japan. Therefore, we have observed the bacterium's abundance in seawater and seaweed samples from three areas of the Kii Channel, Japan, during June 2003 to May 2004. A total of 192 samples were collected: 24 from each source in summer, autumn, winter and spring. The samples were selectively cultivated following the most probable number (MPN) technique. Vibrio vulnificus population ranged from 0 to 10(3) MPN 100 mL(-1) seawater or 10 g seaweeds; higher counts were observed during summer. The optimum temperature, salinity and pH for the bacterium were 20-24 degrees C, 24-28 p.p.t. and 7.95-8.15, respectively. However, seaweeds always contained higher V. vulnificus than seawater. Among 280 V. vulnificus strains, detected by species-specific colony hybridization and PCR, 78, 74, 11 and 16 were from seaweeds and 46, 42, 2 and 11 were from seawater during summer, autumn, winter and spring, respectively. Ribotyping of 160 selected strains revealed a higher genotypic diversity (18 patterns) among strains from seaweeds than from seawater (10 patterns). Seaweeds can thus act as a potential habitat for V. vulnificus and are more unsafe for consumption during summer.